Background

Several studies have shown an increased risk of colorectal and extracolonic cancers for carriers of germline MUTYH mutations inherited from both parents (biallelic mutations). Extracolonic cancer risks for carriers of a MUTYH mutation inherited from only one parent (monoallelic mutation) have not previously been estimated.

Materials and methods

We identified 144 families of MUTYH mutation carriers from three countries that we ascertained through population-based sources of the multi-site, international Colon Cancer Family Registry. Mutation status, sex, age, and histories of cancer, polypectomy, and hysterectomy were sought from 2,179 of their relatives. Using Cox regression weighted to adjust for the method of ascertainment, we estimated the country-, age- and sex-specific standardized incidence ratios (SIRs) of colorectal and extracolonic cancers for monoallelic mutation carriers, compared with the general population, and corresponding age-specific cumulative risks.